Plugs burning too clean on a 165 hp 250 six??

[luva63]

Pulled my plugs out of my 1975 165 hp mercruiser GM straight six last night to check compression and noticed they looked like " brand new" plugs after being run all Summer. The porcelain centers were perfectly white. Been noticing my RPMs were down slightly with lower top speeds. Fuel pump weak?? Any thoughts appreciated. Running AC R 43 T plugs. Compression ran from 120 to 130 with #6 being the 130.Don't really trust my compression gauge.

 

[FreeBeeTony]

Plugs that look like new usually indicate water in the cylinders.

 

[alldodge]

Pulled my plugs out of my 1975 165 hp mercruiser GM straight six last night to check compression and noticed they looked like " brand new" plugs after being run all Summer. The porcelain centers were perfectly white. Been noticing my RPMs were down slightly with lower top speeds. Fuel pump weak?? Any thoughts appreciated. Running AC R 43 T plugs. Compression ran from 120 to 130 with #6 being the 130.Don't really trust my compression gauge.

I think your running lean, need to clean the carb and check fuel pump pressure

 

[stonyloam]

+1 with Tony. Water will "steam clean" the plugs and the insulators will be snow white. If it were just running lean, there should be SOME color on the insulators. A leaking head gasket on mine caused ONE plug to look that way, but for all six the only thing I can think of is water coming in with the fuel. Just a guess.

 

[luva63]

Thanks guys, I don't think( at least hope) there's no water getting in the cylinders. I installed a new manifold last winter so maybe that's not a problem. Low speeds,it runs great and it's no slouch at WOT. Where it was consistently running 46 mph it has now dropped down to 44-45 mph so I didn't think there was much wrong with it. Changed fuel filters (all of them) last winter so that shouldn't be an issue. The motor oil looks new after running it all summer and it don't use a drop that I can tell. I really like my 250 chivy